The present invention relates to a precast concrete silo complex and a method of constructing it. Recently, high quality voluminous silos have been required for storing cereal grains, various raw materials, fodder, etc, and especially silos for grains are required to be highly airtight and structurally safe. As a method of constructing such silos, conventionally, the sliding form method has been considered the best. With the sliding form method, about 1.2 m high inside and outside molds are fixed by a frame called a yoke, and while said molds are raised upward at about 30 cm per hour by a hydraulic jack fitted to said yoke, concrete is poured continuously. In other words, concrete placing and mold releasing occur simultaneously so that a monolithic silo cylinder is produced. This method, compared with the successive concrete placing method makes it possible to obtain high airtightness which is the most important for grains (especially for imported grains) and provides a beautiful appearance, and therefore has been considered the best method as mentioned above. However, while this method can shorten the period of construction, the necessity of working day and night for a short period of time requires working in two or three shifts, and therefore requires many workers and engineers at one time, involving the difficulty of obtaining an adequate working force. In addition to this disadvantage in work control, according to this method, since concrete is directly poured in the field, the quality of the silo cylinder depends upon such natural conditions as weather at the time of pouring, and especially in the rainy or dry season, the quality is greatly affected. Furthermore, the quality control of the concrete itself is very difficult, causing indefinite factors in the quality such as airtightness and strength, which are important for the silo cylinder, which is a further large disadvantage of this method.